Reversing the decline of threatened koala (Phascolarctos cinereus) populations in New South Wales: Using genomics to enhance conservation outcomes

Genetic management is a critical component of threatened species
conservation. Understanding spatial patterns of genetic diversity is
essential for evaluating the resilience of fragmented populations to
accelerating anthropogenic threats. Nowhere is this more relevant than on
the Australian continent, which is experiencing an ongoing loss of
biodiversity that exceeds any other developed nation. Using a proprietary
genome complexity reduction-based method (DArTSeq), we generated a data
set of 3,239 high quality Single Nucleotide Polymorphisms (SNPs) to
investigate spatial patterns and indices of genetic diversity in the koala
(Phascolarctos cinereus), a highly specialised folivorous marsupial that
is experiencing rapid and widespread population declines across much of
its former range. Our findings demonstrate that current management
divisions across the state of New South Wales (NSW) do not fully represent
the distribution of genetic diversity among extant koala populations, and
that care must be taken to ensure that translocation paradigms based on
these frameworks do not inadvertently restrict gene flow between
populations and regions that were historically interconnected. We also
recommend that koala populations should be prioritised for conservation
action based on the scale and severity of the threatening processes that
they are currently faced with, rather than placing too much emphasis on
their perceived value (e.g., as reservoirs of potentially adaptive
alleles), as our data indicate that existing genetic variation in koalas
is primarily partitioned amongst individual animals. As such, the
extirpation of koalas from any part of their range represents a
potentially critical reduction of genetic diversity for this iconic
Australian species.